<?xml-stylesheet href="chrome://browser/skin/" type="text/css"?>
<window xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul" xmlns:html="http://www.w3.org/1999/xhtml">
<box onerror="document.loadOverlay('file:///does-not-exist', null);" >
<html:script src="ftp://some.website.that.will.cause.an.error"/>
</box>
</window>
